'71 Duster gas cap question

From my understanding the '71 gas cap was a one-year-only. '71 Duster 340. I currently have a lockable cap on mine and want to replace it with a paintable, original style. Before I start a WTB ad, can you guys confirm this is in fact the case? And if so, will any A-body '71 cap work, or is that yet another unique aspect of the cap?
- Nick